Method for cementless building of retreaded tires

ABSTRACT

An Apparatus for applying cushion gum to a periphery of a tire casing without cement includes a conveyor having a forward roller near the tire casing. The conveyor is mounted on a carriage that is movable relative to its base so that the conveyor can be moved to contact the tire casing. The conveyor moves the cushion gum below an infrared heater to heat an interface side of the cushion gum to increase its tack and then moves the heated cushion gum between the forward roller and the tire casing. The forward roller of the conveyor applies the cushion gum to the periphery of the tire as the cushion gum exits the conveyor and first contacts the tire casing. A supply roller is provided to move the cushion gum from a supply roll to the rear end of the conveyor. A cutting mechanism is provided between the supply roller and the conveyor to selectively cut the cushion gum.

This is a divisional of application Ser. No. 08/412,458, filed Mar. 29,1995, now U.S. Pat. No. 5,635,015.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for cementless building ofretreaded tires, and more particularly, to an apparatus that heats andapplies cushion gum material to a tire casing.

2. Description of Related Art

In a tire retreading process, a strip or web of rubber bonding materialor cushion gum is applied to the periphery of a buffed tire casing.Typically a cement, such as a rubber/hydrocarbon solvent solution, isfirst applied to the tire casing to provide the necessary tack to firmlyhold the cushion gum material to the tire casing during subsequentstitching, tread application, and curing. The step of applying cement iscostly and time consuming because the cement must be applied and allowedto dry before the cushion gum material can be affixed. Additionally, theuse of solvent based cements or adhesives can cause safety andenvironmental concerns.

The cement can be eliminated from the process by heating the cushion gummaterial because the tack of a rubber compound, such as the cushion gummaterial, increases as it is heated. One approach has been to warmentire rolls of the cushion gum in an oven. This approach, however, cancause a decrease in material shelf life due to the short scorch time ofthe cushion gum material. This is particularly a problem if the materialis not used promptly after heating.

Another approach has been to heat the cushion gum material as it isbeing applied to the tire casing. For example, see U.S. Pat. No.4,096,008, the disclosure of which is expressly incorporated herein inits entirety by reference, disclosing a method of manufacturing andretreading tires. The cushion gum material is pulled from a supply roll,heated at an outer surface, pulled around and applied to the tirecasing, and subsequently pressured by rollers to the tire casing.Heating the cushion gum material at an outer surface to increase theamount of tack at an inner surface can result in overheating orscorching the cushion gum material. Additionally, tensioning the cushiongum material can stretch the cushion gum material and result in anuneven thickness. Furthermore, applying and pressuring the cushion gumto the tire casing in separate steps can result in entrapped air betweenthe tire casing and the cushion gum material. Accordingly, there is aneed in the art for an improved apparatus for cementless building ofretreaded tires.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for applying cushion gum toa periphery of a tire casing that solves the above-noted problems of therelated art. The apparatus according to the invention includes a heaterfor heating the cushion gum and a conveyor for moving the cushion gumnear the heater such that an interface side of the cushion gum isheated. The apparatus also includes a roller adjacent the periphery ofthe tire and means for moving the roller against the tire casing. Theconveyor moves the heated cushion gum between the roller and the tirecasing so that the heated cushion gum is pressured to the tire casing asthe interface side of the cushion gum first contacts the tire casing.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further features of the present invention will be apparentwith reference to the following description and drawings, wherein:

FIG. 1 is an elevational view an apparatus for cementless building ofretreaded tires according to the present invention;

FIG. 2. is a plan view of the apparatus of FIG. 1;

FIG. 3 is a sectional view taken along line 3--3 of FIG. 1;

FIG. 4 is an elevational view taken along line 4--4 of FIG. 1; and

FIG. 5 is an elevational view of the apparatus of FIG. 1 with thecarriage moved toward the tire casing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an apparatus 10 for applying cushion gum material 12 to theperiphery of a tire casing 14 according to the present invention. Theapparatus 10 includes a frame 16 having a tire support 18, a base 20,and a movable carriage 22. The tire support 18 includes an expandablehub 24 for engaging and rotatably supporting the tire casing 14 about ahorizontal and transverse axis of rotation.

The base 20 includes a pair of longitudinally extending horizontalsupports 26. As seen in FIGS. 1 and 4, the carriage 22 includes fourpairs of rollers 28, 30. Two pairs of the rollers 28, 30 are located ateach horizontal support 26 of the base 20. Each pair of rollers 28, 30is spaced about one of the horizontal supports 26 so that an upperroller 28 is in rolling contact with an upper surface of the horizontalsupport 26 and a lower roller 30 is in rolling contact with a lowersurface of the horizontal support 26. Positioned in this manner therollers 28, 30 guide and support the carriage 22 so that the carriage 22is movable in a longitudinal direction relative to the base 20 towardand away from the tire support 18.

An indexing means 32 is provided between the carriage 22 and the base 20for moving the carriage 22 toward and away from the tire casing 14. Theindexing means 32 of the illustrated embodiment is a pneumatic or aircylinder. The air cylinder is mounted in a longitudinal directionbetween angle supports 34, 36 attached to the carriage 22 and the base20. It will be noted that other indexing means 32 for moving thecarriage 20 could be utilized such as, for example, a rack and pinion, aspring mechanism, a hydraulic cylinder, or an electric motor.

As best seen in FIG. 4, the carriage 22 also includes a swinging bar 38at a rear end of the carriage 22. The swinging bar 38 has a transverselyextending horizontal portion 40 for holding a cushion gum materialsupply roll 42 and upwardly extending vertical portions 44 at ends ofthe horizontal portion 40. The cushion gum material 12 on the supplyroll 42 is a relatively thin sheet and typically has a polyethylene filmor liner on its outer side to prevent the cushion gum material 12 fromsticking to itself. The supply roll 42 is supported by the horizontalportion 40 of the swinging bar 38 so that the supply roll 42 rotates asthe cushion gum material 12 is pulled from the supply roll 42. An upperend of each vertical portion 44 is hingedly attached to the carriage 22so the swinging arm 38 pivots about a transversely extending horizontalaxis. The swinging bar 38 thereby minimizes tensioning or stretching ofthe cushion gum material 12 as it is pulled from the supply roll 42.

As best seen in FIGS. 1 and 2, a supply roller 46 is mounted on thecarriage 22 at the rear end of the carriage 22 and above the supply roll42 of cushion gum material 12. The supply roller 46 has an associatedpinch or pressure roller 48 located at its upper side. The pressureroller 48 must supply enough pressure so that the cushion gum material12 is pulled off of the supply roll 42, yet not enough pressure to stickor adhere to the cushion gum material 12. A cam lever 50 is provided toraise the pressure roller 48 and remove the pressure so that no cushiongum material 12 is pulled from the supply roll 42.

The cam lever 50 downwardly pivots about a forward pivot point 52 sothat a rear end downwardly cams a forward end of a pressure rollersupport 54. The pressure roller support 54 pivots about a central pivotpoint 56 so that a rear end of the pressure roller support 54 rotatesupwardly to raise the pressure roller 48 away from the supply roller 46.

A heater conveyor 58 is mounted to the carriage 22 at a forward end ofthe carriage 22. The heater conveyor 58 is positioned so that thecushion material 12 is moved to the forward end of the carriage 20 in agenerally horizontal path. The heater conveyor 58 includes horizontallyextending forward and rear rollers 60, 62 and an endless belt 64. Therear roller 62 has an associated pinch or pressure roller 66 located atits upper side. The pressure roller 66 must supply enough pressure sothat the cushion gum material 12 is pulled onto the heater conveyor 58,yet not enough pressure to stick or adhere to the cushion gum material12. A centerline 68 of the heater conveyor 58 generally intersects therotational axis of the tire casing 14 as seen in FIG. 1. The heaterconveyer 58 can also include a suction device 70 to hold the cushion gummaterial 12 on the endless belt 64 of the heater conveyor 58 to preventor minimize bunching and/or tensioning of the cushion gum material 12.

The heater conveyor 58 extends through an oven or heater 72. The heater72 includes a series of infrared heating elements 74 which arepositioned above the heater conveyor 58 to heat the cushion gum material12 as it is carried through the heater 72 by the heater conveyor 58. Theinfrared heating elements 74 can be of any suitable type such as, forexample, incandescent quartz heat lamps. The heating elements 74 arecontrolled with a thermocouple 76 to heat the cushion gum material 12 toa temperature at which the tack of the cushion gum material 12 isincreased but the cushion gum material 12 is not overly softened orscorched. The temperature is preferably in the range of about 100degrees Fahrenheit (F.) to about 200 degrees F. and is more preferablyabout 150 degrees F. It will be noted that the cushion gum material 12passes under the heating elements 74 such that an interface side of thecushion gum material 12, that is a side of the cushion gum material 12that will contact the periphery of the tire casing 14, is heated.Heating the interface side minimizes the amount of heat required for theinterface side to become tacky, and therefore, the interface sidebecomes tacky without scorching the cushion gum material 12 and withoutoverly softening the cushion gum material 12 so that it is vulnerable tostretching.

As best seen in FIGS. 2 and 3, a cutting anvil 78 is located between thesupply roller 46 and the heater conveyor 58 to provide a smoothtransition between the supply roller 46 and heater conveyor 58 and alsoprovide a suitable surface for cutting the cushion gum material 12. Thecutting anvil 78 includes a substantially flat plate 80 mountedgenerally horizontal at a height generally equal to an upper surface ofthe supply roller 46 and the heater conveyor 58. A cutting mechanism 82is located between the supply roller 46 and the heater conveyor 58 andis aligned with the cutting anvil 78. The cutting mechanism 82 of theillustrated embodiment includes a rotary cutter 84 and a transverselyextending air cylinder 86 for transversely moving the rotary cutter 84across the cutting anvil 78 to shear the cushion gum material 12. Itwill be noted that other cutting mechanisms 82 could be utilized suchas, for example, a hot wire or a shearing knife.

As best seen in FIG. 1, the supply roller 46 and heater conveyor 58 aredriven by a drive motor 88 and a series of drive chains and sprockets.The single drive motor 88 enables the cushion gum material 12 to bemoved without causing tensioning or stretching of the cushion gummaterial 12. The drive motor 88 is mounted to the carriage 22 near theforward end of the carriage 22. The drive motor 88 is preferably a D.C.gear motor capable of conveying the cushion gum material 12 at a speedof about 0.5 feet/second to about 2 feet/second. A first drive chain 90extends from a sprocket 92 driven by the drive motor 88 and a firstsprocket 94 mounted on the forward roller 60 of the heater conveyor 58.A second drive chain 96 extends from a second sprocket 98 mounted on theforward roller 60, a sprocket 100 mounted to the rear roller 62 of theheater conveyor 58, and a sprocket 102 mounted on the supply roller 46.The second drive chain 96 is kept in constant tension by a tensioningdevice or sprocket 104 as known in the art.

To apply the cushion gum material 12, the tire casing 14 is installed onthe expandable hub 24 and inflated with air to a pressure of about 10 toabout 30 psig. The carriage 22 is then indexed toward the tire casing 14by supplying air to the air cylinder 32 until the forward roller 60 ofthe heater conveyor 58 contacts and sufficiently deflects the tirecasing 14 to flatten a crown on the periphery of the tire casing 14 asbest seen in FIG. 5. Typically about 10 to about 30 pounds of pressureare applied. This procedure allows the apparatus 10 to apply cushion gummaterial 12 to any size of tire casing 14.

The end of the cushion gum material 12 is pulled up to the supply roller46 and fed between the pressure roller 48 and the supply roller 46 andacross the cutting anvil 78 to the cutting mechanism 82. In thisposition the liner side of the cushion gum material 12 is contacting thecutting anvil 78 and the interface side of the cushion gum material 12,that is the side that will contact the tire casing 14, is facing upward.The cutting mechanism 74 is activated and the air cylinder 86 moves therotary cutter 84 across the cushion gum material 12 to cut an evenstarting edge. The rotary cutter 84 is then returned to its homeposition. This initial cutting operation is only necessary with a newsupply roll 42 of cushion gum material 12 or if the end of the cushiongum material 12 is damaged.

The drive motor 88 is activated and the cushion gum material 12 movesunder the pressure roller 66 of the heater conveyor 58 and onto theendless belt 64 of the heater conveyor 58 and is moved through theheater 72 at a speed of about 0.5 to 2 feet/second. As the cushion gummaterial 12 passes through the heater 72, the infrared heating elements74 heat the interface side of the cushion gum material 12 to about 150degrees F. or at least a temperature where the interface side of thecushion gum material 12 becomes tacky. The heated cushion gum material12 exits the heater 72 and passes over the forward end of the heaterconveyor 58 and immediately onto the inflated tire casing 14 which isrotating at the same surface velocity as the heater conveyor 58. Theforward roller 60 of the heater conveyor 58 applies the cushion gummaterial 12 with pressure, that is, presses the cushion gum material 12onto the periphery of the tire casing 14. The combination of heat andpressure bonds the cushion gum material 12 to the tire casing 14 andforces out any trapped air. It is noted that the cushion gum material 12does not contact the periphery of the tire casing 14 until it is pressedor pressured onto the tire casing 14 by the forward roller 60. It isalso noted that the cushion gum material 12 is not tensioned once it hasbeen heated so that the cushion gum material 12 is not stretched and aneven thickness is maintained.

The drive motor 88 is stopped after a predetermined period of time. Thepredetermined period of time is equal to the time required for apredetermined length of cushion gum material 12, the length required tocover the periphery of the tire casing 14, to pass the cutting mechanism82. Once the drive motor 88 is stopped, the cutting mechanism 82 isactivated to cut the cushion gum material 12 at the predeterminedlength, as described above. It is noted that the cutting time must bekept to a minimum, preferably less than 10 seconds, so that the cushiongum material 12 in the heater 72 does not deteriorate. Alternatively,the temperature of the heater 72 can be controlled during the cuttingdelay so that the cushion gum material 12 remaining in the heater 72 isnot overheated or scorched.

When the cutting cycle is complete, the drive motor 88 is activated andthe remainder of the cut length of cushion gum material 12 is applied tothe tire casing 14. Prior to activating the drive motor 88, the camlever 50 is activated to disengage the pressure roller 48 from thesupply roller 46 so that a new length of cushion gum material 12 is notfed into the heater 66. It will be noted that if the heater conveyor 58is sized to hold full a length of material for the tire casing 14, thecutting operation takes place prior to beginning to apply the cushiongum material 12 to the tire casing 14. It will also be noted that if aprecut length of cushion gum material 12 is used the drive motor 88 doesnot need to be stopped during the application of the cushion gum 12.

Once the cushion gum material 12 is applied to the entire periphery ofthe tire casing 14, the drive motor 88 is stopped and the carriage 22 ismoved away from the tire casing 14. The above cycle is repeated when itis desired to apply the cushion gum material 12 to another tire casing14.

Although a particular embodiment of the invention has been described indetail, it will be understood that the invention is not limitedcorrespondingly in scope, but includes all changes and modificationscoming within the spirit and terms of the claims appended hereto.

What is claimed is:
 1. A method for applying cushion gum to a peripheryof a tire casing, said method comprising the steps of:(a) conveying andsupporting cushion gum on a generally horizontal conveyor with a tirecasing interface side of the cushion gum facing away from the conveyor;(b) cutting the cushion gum to a predetermined length corresponding tothe periphery of the tire casing; (c) heating the cushion gum to atemperature at which the cushion gum becomes tacky with heating elementspositioned above the conveyor and directly facing the interface side ofthe cushion gum; and (d) applying and pressuring the cushion gum to theperiphery of the tire casing with a forward roller of the conveyor asthe cushion gum exits the conveyor and first contacts the tire casing.2. The method according to claim 1, wherein the cushion gum is heated toa temperature in the range of about 100 degrees Fahrenheit to about 200degrees Fahrenheit.
 3. The method according to claim 2, wherein thecushion gum is heated to a temperature of about 150 degrees Fahrenheit.4. The method according to claim 1, wherein the cushion gum is appliedat a speed in the range of about 0.5 to about 2.0 feet per second. 5.The method according to claim 1, wherein the cushion gum is applied witha pressure in the range of about 10 pounds to about 30 pounds.
 6. Themethod according to claim 1, wherein the step of cutting the cushion gumto the predetermined length includes cutting the cushion gum before thecushion gum is heated by the heating elements.
 7. The method accordingto claim 6, wherein the step of cutting the cushion gum to thepredetermined length includes cutting the cushion gum before the cushiongum enters the conveyor.
 8. The method according to claim 7, wherein thestep of cutting the cushion gum to the predetermined length includessupporting the cushion gum with a cutting anvil.
 9. The method accordingto claim 1, wherein the step of heating the cushion gum includes heatingthe cushion gum with infrared heating elements.
 10. The method accordingto claim 1, further comprising the step of pulling the cushion gum froma supply roll with a pinch roller.
 11. The method according to claim 10,further comprising the step of supporting the cushion gum between thepinch roller and the conveyor.